Solving electrical connector problems

Though typically an inexpensive part, a connector that malfunctions can cause catastrophic failures and enormous expense. 

In June 2019, a connector failure forced Mazda to recall nearly 8,300 sports utility vehicles in the U.S. and Canada. The vehicles had passed final factory inspection—but once in the hands of customers, a defective wiring harness connector developed excessive electrical resistance. 

The failure of that single, simple part illuminated warning lights, generated diagnostic error codes, and became an expensive headache for the manufacturer. Other connector failures have caused major power outages and crashed planes. A connector failure nearly doomed the final Mir space station module just after it reached orbit.

The most common connector failure mechanisms are mechanical failure (parts break or lose adhesion) and corrosion of metal contacts. Metal contact pins are vulnerable to moisture ingress through the metal-plastic interface between the pins and injection molded housing. Moisture corrodes the pins and degrades component adhesion.

Plasma is a state of matter in which a natural or manufactured process energises a gas to the point that it ionises. Manufacturers have treated surfaces with plasma for decades, as an alternative to grit blasting, laser etching, and chemical processes. Plasmatreat is a global leader in plasma-based surface modification and functional coating—providing solutions that require no vacuum equipment, curing, or toxic chemical baths. Plasmatreat solutions can activate or coat a part in seconds, usually using air instead of costly gases. Precursor (chemical) consumption is low, < 50g/hour. Plasma has multiple capabilities that help prevent electrical connector failure:

• Cleaning: Plasma energy is extremely effective at breaking most organic molecular bonds. It provides an efficient and environmentally friendly way to remove organic particulates and oils from electrical contacts and other surfaces.
• Activation: Plasma treatment can change surface properties such as wettability, enhancing adhesion strength, such as when bonding a metal contact to a plastic connector block.
• Coating: In more recent advances, Plasmatreat has developed a proprietary method (PlasmaPlus) that applies various nano-coatings. These coatings include: 
  • Corrosion barriers that replace toxic Cr6 primers with stable, long-term protection for metals such as aluminium alloys and titanium
  • Bonding and sealing layers that promote direct adhesion of dissimilar materials without primers and adhesives

Plasmatreat and a group of other industry specialists, Arburg, Akro-Plastic, Cobes, and Kegelmann Technik, have teamed up to produce a prototype multi-pin electrical connector. The result demonstrates the efficacy of plasma as a manufacturing step that greatly increases connector quality and reliability.

For its part in this team effort, Plasmatreat developed a new process in which a robot uses an open-air plasma jet to clean and activate the connector pins and the plastic sub-assembly that houses them. The robot then spins the pin assembly around to a second plasma jet that uses Plasmatreat’s PlasmaPlus technology to apply a nano-coating bonding agent.

This second step is an advanced form of chemical vapour deposition (CVD). A plasma jet delivers and adheres Plasma-SealTight (PST), a dry primer that promotes adhesion while sealing the metal surface against corrosion. The cleaned, activated, and coated part is then ready for a subsequent step that injection molds it into the connector housing, replacing the need for potting. The plasma treatment results in a high integrity, high reliability assembly, with no voids between electrical contacts and plastic compound connector body.

The finished product is a robust connector that provides superior electrical conduction, prevents corrosion, and resists up to 5 bars (72 PSI) of water incursion—equivalent to immersion in 50 meters (165 feet) of water.

Vastly improving the plastic-metal bond and corrosion resistance in an electrical connector is a specific example that illustrates only some of the many advantages of plasma. Advanced plasma technology is a tool with application across many industries. Nearly any manufacturing process that requires critical surface preparation can find a better, cheaper, and safer solution in plasma surface treatments. Plasma surface preparation can:

• Replace toxic solvents and primers with low quantities of comparatively safe compounds
• Clean surfaces and deposit special coatings in the same step
• Treat surfaces to better receive adhesives and coatings
• Apply nano-coatings (PlasmaPlus) that create specific surface properties, such as hydrophobic, anti-corrosive, adhesion promoting

Plasmatreat’s precision processes and ISO 9001:2015 certification ensure high quality and reliable repeatability.